Photodiode detectors typically include one- or two-dimensional arrays of electrically-patterned detector elements in a semiconductor material. The photodiode detector is in electrical communication with a device, e.g., a camera, and is used to detect electromagnetic radiation (e.g., infrared light, visible light, ultraviolet light, etc.). Photodiode detectors made from antimonide III-V semiconductor materials are emerging as a competitive alternative material system to InGaAs and HgCdTe semiconductor materials for detection of infrared electromagnetic radiation. Examples of antimonide III-V semiconductor materials are GaInAsSb quaternary alloys and InAs/Ga(In)Sb short period superlattices. GaInAsSb quaternary materials have cut-off wavelengths ranging between about 1.7 to 4.9 microns. InAs/Ga(In)Sb short period superlattices have cut-off wavelengths between 2 to 30 microns. Cameras operating at these wavelengths are important in such applications as point chemical sensing (medical and environmental), thermal imaging (military and security), astronomy, and food monitoring.
The electrically-isolated detector elements are presently formed with a “mesa” manufacturing technique. In this technique, a doped semiconductor material (e.g., p-GaSb) is epitaxially grown over an oppositely-doped semiconductor material (e.g., n-GaSb) to form a p-n (or a n-p) junction. The detector elements are patterned by conventional photolithography and then etched to form “mesa” structures.
A known problem with the “mesa” manufacturing technique is that the etch process damages (e.g., by undercutting) the mesa sidewalls, resulting in significant current leakage (e.g., by generation-recombination current leakage). Current leakage limits detector performance as the size of the detector element shrinks. To minimize sidewall leakage and stabilize detector performance, additional processing steps are required to chemically clean, passivate, and encapsulate the mesa sidewalls. Accordingly, it is desirable to improve detector performance by reducing current leakage through mesa sidewalls. It is further desirable to reduce manufacturing time and costs by reducing the number of manufacturing steps required to form detector elements.